1. Field of the Invention
This invention relates to an apparatus for use in the repairing of thermoplastic underground utility pipes and, in particular, service tees. This invention further relates to an apparatus for use in repairing thermoplastic underground utility service tees from above ground through keyhole and similar minimal excavations.
2. Description of Related Art
Aldyl “A”, also referred to as Aldyl A polyethylene, is one of several thermoplastic materials which has been used for many years to produce pipes for gas utility distribution systems. Piping systems made of thermoplastic materials such as Aldyl A have enjoyed widespread popularity due primarily to the ease with which such systems may be fabricated and installed. Pipe made of thermoplastic materials are lightweight, corrosion resistant, strong and durable. However, many thermoplastic gas distribution systems which have been in service for several years are experiencing problems with leaking joints and service tees. The leaks occurring in service tees typically are due to the failure of the threaded insert that secures the tee cap to the tee. Failure of the threads causes the cap to loosen or even come off of the tee, allowing gas that seeps past the tee coupon to escape into the surrounding soil. One method for addressing this problem involves the installation of an electrofusion coupling with a new cap. However, this method requires reducing the outer diameter of the tee to the proper size for accepting the electrofusion coupling.
“Keyholing” and “potholing” refers to the excavation of a hole to access or repair utilities. Potholing and keyholing are preferred over other techniques such as digging shovels, backhoes, and the like which often result in damage to the utilities and the corresponding demand for expensive repair and reconstruction. In addition to the increased costs associated with damage repair and increased labor costs associated with digging, such damage may present danger to workers or others in the immediate vicinity of the excavation. Typically, a keyhole is 12-18 inches in diameter and up to about ten feet in depth and visibility down the keyhole is limited, thereby precluding the use of conventional tools to access the utility. Thus, apparatuses for in-ground repairing of utility distribution systems must be capable not only of installation from above ground, but also of operation from above ground.